For medical reasons, in vivo parameters of a patient may need to be monitored over a period of time. Heart arrhythmias are changes in the normal sequence of electrical impulses that cause the heart to pump blood through the body. Continuous monitoring may be required to detect arrhythmias because abnormal heart impulse changes might only occur sporadically. With continuous monitoring, medical personnel can characterize cardiac conditions and establish a proper course of treatment.
One prior art device that measures heart rate is the “Reveal” monitor by Medtronic (Minneapolis, Minn., USA). This device comprises an implantable heart monitor used, for example, in determining if syncope (fainting) in a patient is related to a heart rhythm problem. The Reveal monitor continuously monitors the rate and rhythm of the heart for up to 14 months. After waking from a fainting episode, the patient places a recording device external to the skin over the implanted Reveal monitor and presses a button to transfer data from the monitor to the recording device. The recording device is provided to a physician who analyzes the information stored therein to determine whether abnormal heart rhythm has been recorded. The use of the recording device is neither automatic nor autonomic, and therefore requires either the patient to be conscious or another person's intervention to transfer the information from the monitor to the recording device.
Another known type of implantable monitoring device is a transponder-type device, in which a transponder is implanted in a patient and is subsequently accessed with a hand-held electromagnetic reader in a non-invasive manner. An example of the latter type of device is described in U.S. Pat. No. 5,833,603.
A sensing device and a method of acquiring signals and computing measurements according to one embodiment of the invention are disclosed herein. The sensing device comprises a sensor assembly and a computing device. The sensor assembly includes a plurality of emitters and a plurality of detectors for generating a plurality of signals. The emitters and detectors face one side of a vessel. A computing device operates the plurality of emitters and detectors and processes the plurality of signals to obtain measurement values. The sensor assembly and the computing device are enclosed in a housing.
One embodiment of a method according to the invention includes the steps of providing a sensor device such as the one described in the paragraph above, operating the plurality of emitters and detectors to obtain a plurality of signals, processing the signals to obtain measurement values, and analyzing the measurement values to obtain parameter values indicative of a characteristic of at least one of the vessel and the fluid.
Another embodiment according to the invention discloses a device for optically measuring a characteristic of at least one of a blood vessel and blood flowing through the blood vessel. The device includes a housing, a sensor assembly, and a computing device. The sensor assembly is mounted to the housing and includes a plurality of emitters for emitting photons through a first side of the housing and a plurality of detectors for receiving at least a portion of the emitted photons through the first side of the housing. Each emitter is operationally paired with a separate detector and oriented such that a beam of photons emitted from the emitter that impinges upon a vessel adjacent the sensor assembly will partially reflect toward the paired detector, each detector being configured to produce a signal representing the emitted photons received by the detector. The computing device is configured to activate the plurality of emitters and interpret the signals from the detectors to determine the characteristic.
The features of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings.
Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention in several forms and such exemplification is not to be construed as limiting the scope of the invention in any manner.